(Reuters Health) - Pregnant women who have both severe obesity and diabetes may be more likely to have children with autism, ADHD and other psychiatric disorders than mothers who don’t have either condition during pregnancy, a new study suggests.

Even without diabetes, severely obese mothers were 67 percent more likely to have children with mood and stress disorders than women who maintained a healthy weight during pregnancy, the study found.

With preexisting diabetes, obese mothers were more than six times as likely as other women to have children with ADHD, conduct issues or autism. These kids were also more than four times as likely to have emotional disorders.

“We found marked risks only for mothers with both severe obesity and insulin-treated diabetes,” when they became pregnant, said senior study author Catharina Lavebratt, a researcher at Karolinska University Hospital in Sweden.

“Diabetes with onset during the pregnancy did not imply any marked effect on the risk for psychiatric disorder in the children,” Lavebratt said by email.

While the absolute risk of these problems was low - for example less than 1 percent of the children had autism or ADHD - the results offer fresh evidence that the combined impact of obesity and diabetes on offspring may be worse than either condition on its own, the authors write in Pediatrics.

For the study researchers examined data on almost 650,000 live births in Finland between 2004 and 2014. They followed children from birth through the end of the study, up to age 11 years in some cases.

Mothers were a healthy weight at the start of the majority of these pregnancies. But they were overweight 21 percent of the time, obese in nearly 8 percent of cases and severely obese in almost 4 percent of the pregnancies.

Only 4,000 women, or less than 1 percent, had diabetes when they conceived. Researchers focused only on women with type 2 diabetes, which is associated with obesity.

Overall, almost 35,000 kids, or about 5.4 percent, were diagnosed with a psychiatric disorder during the study period. This total included developmental delays in things like speech and motor skills in addition to conditions like autism, conduct disorders or ADHD.

Obese mothers were 69 percent more likely than normal-weight women to have kids with neurodevelopmental disorders and 88 percent more likely to have children with attention-deficit/hyperactivity disorder (ADHD) or conduct problems.

The study wasn’t designed to prove whether or how obesity or diabetes alone or in combination might make women more likely to have children with psychiatric problems.

Another limitation, the authors note, is that they only followed babies born later in the study for a short period of time.

In addition, the study only counted women as diabetic if they were prescribed insulin, which is usually reserved for more severe cases. Researchers also identified obesity at one point in time, and the amount of weight women gain during pregnancy may independently influence children’s risk of many physical and mental health problems.

Still, the results underscore the potential for a range of neurodevelopmental disorders to have environmental origins that could potentially be predicted and prevented in some cases, said Dr. Xiaobin Wang, director of the Center on the Early Life Origins of Disease at Johns Hopkins University in Baltimore.

“Reproductive age women can take an active role in maintaining a healthy lifestyle and a healthy weight,” Wang, who wasn’t involved in the study, said by email.

“Pregnant women can adhere to gestational weight gain and healthy pregnancy recommendations,” Wang added. “And newborns’ future risk can be evaluated and preemptive interventions could be initiated early in life.”